Reduction of thymine radicals by Tryptophan: A study of CIDNP kinetics

•Thymine radical intermediates were characterized by time-resolved chemically induced dynamic nuclear polarization (CIDNP).•PCET from neutral thymine to triplet benzophenone in neutral solution leads to the formation of a neutral thymine radical.•Formation of an elusive cationic thymine radical on the geminate stage of the reaction was revealed by time-resolved CIDNP.•At pH 11.7, electron transfer leads primarily to neutral thymine radical, that deprotonates rapidly to thymine radical anion.•Reduction of thymine radicals by tryptophan was revealed and the rate constants kr, were determined in a wide range of pH.